The present invention relates to a cooling structure of an engine, and particularly to a cooling structure of an engine which includes a spacer inserted into a water jacket of a cylinder block of the engine.
Generally, vehicles with an engine are formed with water jackets for flowing coolant in the engine cylinder block and cylinder head. The coolant is introduced from the cylinder block at one end in a cylinder line-up direction into the water jacket of the cylinder block, and circulated inside the water jacket of the cylinder block and then into the water jacket of the cylinder head, so as to cool the part of the engine near combustion chambers.
Generally, the coolant circulated inside the water jackets of the cylinder block and the cylinder head is discharged to a radiator from the cylinder head at the other end in the cylinder line-up direction, cooled by the radiator, and then introduced into the water jacket of the cylinder block again from the one end of the cylinder block by a water pump.
In the case of cooling by the circulation of the introduced coolant to the water jackets of the cylinder block and the cylinder head as described above, an upper part of an inner wall of the water jacket of the cylinder block near the combustion chambers increases in temperature more than a lower part thereof. Therefore, the upper part is required to be cooled more than the lower part.
For example, JP2015-108346A discloses a structure in which a spacer having a vertical wall surface is inserted into a water jacket of a cylinder block to surround cylinder bores. Coolant is introduced from a coolant inlet formed in an outer wall of the water jacket of the cylinder block, and the coolant flow is rectified so that the coolant flows on an outer circumferential side of the vertical wall surface of the spacer in a lower part of the water jacket and also flows on an inner circumferential side of the vertical wall surface of the spacer in an upper part of the water jacket. Thus, an upper part of an inner wall of the water jacket of the cylinder block is cooled more than a lower part thereof.
Further, the vehicles with the engine require a boosted engine warm-up in a cold start and a quick finish of the warm-up in view of fuel consumption and exhaust emission performances, while cooling the upper part of the inner wall of the water jacket of the cylinder block near the combustion chambers more than the lower part.
When the coolant is introduced from the coolant inlet to the outer circumferential side of the vertical wall surface of the spacer in the water jacket of the cylinder block, it may flow into a section between the vertical wall surface of the spacer and the inner wall of the water jacket of the cylinder block from the lower side of the spacer. Thus, the coolant may excessively cool the lower part of the inner wall of the water jacket of the cylinder block and the engine warm-up in the cold start may not be finished quickly enough.
The structure disclosed in JP2015-108346A is provided with a guide part extending toward the coolant inlet in a vertical center part of the vertical wall surface of the spacer to reduce the coolant flow into the inner circumferential side from the lower side of the spacer after being introduced from the coolant inlet. However, the coolant introduced from the coolant inlet along the guide part may flow around the vertical wall surface as well as flow downwardly on both sides of the guide part, and reach between the vertical wall surface of the spacer and the inner wall of the water jacket of the cylinder block from the lower side of the spacer. For this reason, a further improvement is desired.